Ball nose end mills are known in the art in various forms none of which provides high positive rake combined with dovetail pockets for secure insert retention. The closest known prior art involves square or triangular "on-edge" inserts retained by a central screw urging side walls against obtuse angled matching pocket walls. A square insert design of this type is available under the tradename "Ingersoll MAX-I" and a triangular indexable form is disclosed in U.S. Pat. No. 4,618,296. In each case, the holddown screw is subjected to considerable stress under the combination of centrifugal feed and tangential forces particularly since a component of the obtuse reaction support surface of the pocket walls extends in an outward direction.